Chevrolet Cobalt Service & Repair Manual: Diagnosis & Testing

Chevrolet Cobalt Service & Repair Manual / Technical Service Bulletins / Diagnosis & Testing

Accessing Diagnostic Trouble Codes

Connect a suitably programmed scan tool to Data Link Connector (DLC) and follow manufacturers instructions.

Diagnostic Tests

Low tire pressure in one or more tires is indicated by a continuously illuminated TPMS indicator after the bulb inspection is completed. The DIC will display a check tire pressure type message, if equipped. It is not required to perform the relearn procedure for a low tire condition.
When a TPMS DTC is set, the TPMS indicator will flash for one minute after the bulb inspection is completed and then will remain illuminated. The DIC will display a service tire monitor type message, if equipped.
Temperature can effect tire pressure. Low temperature may cause a low tire pressure causing the TPMS indicator to turn On. The air pressure in the tire will increase as the ambient temperature rises or as the tire warms up while the vehicle is driven. The pressure may increase enough to exceed the low pressure threshold which will turn Off the TPMS indicator.
Aftermarket wheel valve stem holes may be located further from the wheel rim than the original equipment wheels. When using the GM TPMS tool, or equivalent, to activate a sensor, ensure the tools antenna is no further than six inches from the sensor and is facing upward. Aftermarket wheel value stem locations can also cause a sensor to not function correctly.
The use of other than GM approved tire sealants can obstruct the sensor pressure sensing port and cause inaccurate tire pressure readings. If this condition is verified, remove the sealer from the tire and replace the tire pressure sensor.
The sensor transmissions may not be received by the RCDLR due to RF interference from items such as aftermarket ignition systems, DVD players, CB radios or metallic type window tinting.
The sensor activation procedure may have to be repeated up to three times before determining a sensor is faulty.
The sensors may become dislodged due to tire rotations where the sensor relearn procedure was not performed or stray sensor transmissions have been received from other vehicles. Always relearn the sensors to ensure the DTC is set.

Diagnostic System Inspection

1. Before performing diagnostic procedures, proceed as follows:
  a. Ensure that battery is fully charged and cable connections are clean and tight.
  b. Inspect fuse panel for blown fuses.
  c. Ensure ground connections are clean and tight.
  d. Inspect system component for wear and damage.
  e. Ensure system electrical connector connections are clean and tight.
  f. Inspect for aftermarket devices that could effect TPMS operation.
2. Connect a suitably programmed scan tool and verify scan tool powers up.
3. Put ignition switch in ON position with engine Off, verify scan tool communicates with all control modules.
4. Access "Power Mode" parameter on scan tool. Verify power mode parameter matches all ignition switch positions.
5. Do not clear any DTCs unless instructed to do so by a diagnostic procedure.
6. Advance to "List All DTCs" screen on scan tool selections to obtain DTCs from each of vehicle modules. Verify there are no DTCs reported from any module. If DTCs are present, diagnosis DTCs in order in which they are displayed on scan tool.

DTC C0569 System Configuration Error

If the tire type and tire pressure information has not been entered during the RCDLR setup, the TPMS indicator on the instrument cluster will flash for one minute and then remain On after the ignition switch has been placed in the ON position and the TPMS warning lamp bulb inspection has been completed. The DIC, if equipped, will also display a "service tire monitor" type message. The DIC will also display the suspect tire pressure as dashes. Under these circumstances, the DTC C0569 will be set and the tire type and tire pressure information will require to be entered for the TPMS to function properly.
A current DTC will clear when the Relearn Procedure has been performed and one ignition cycle has occurred. A newly replaced remote control door lock receiver will set DTC C0569 on its initial ignition ON cycle. The Relearn Procedure must be performed to clear the DTC.
If the DTC resets after performing the Relearn Procedure, replace the RCDLR.

DTC C0750 Left Front Low Tire Pressure Sensor, C0755 Right Front Low Tire Pressure Sensor, C0760 Left Rear Low Tire Pressure Sensor Or C0765 Right Rear Low Tire Pressure Sensor

The TPMS has a radio frequency transmitting pressure sensor in each wheel assembly. As vehicle speed increases, centrifugal force closes the sensors internal roll switch, which puts the sensor into the drive mode. The RCDLR receives and translates the data contained in the tire pressure sensor transmission into sensor presence, sensor mode, and tire pressure. Once the vehicle speed is 25 mph or greater, the RCDLR waits for the first sensor to go into drive mode, then inspects if all sensors have gone into drive mode. If one or more sensors does not go into the drive mode or does not transmit, the RCDLR will set DTC C0750, C0755, C0760 or C0765.
The DIC will display the "Service Tire Monitor" message when the DTC(s) are present. The DIC will also display the suspect tire pressure as dashes. A current DTC will clear when the fault is no longer present and one ignition cycle has occurred. The RCDLR automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
1. Connect GM tool No. EL-46079/J-46079, or equivalent, activate each tire pressure sensor and record each sensors transmission data and physical location. Tool should display eight digit identification number, accurate tire pressure within four psi, "Learn Mode" and good signal strength. If any of parameters are not displayed, replace suspect tire pressure sensor.
2. Connect scan tool, verify that tire pressure sensors identifications and locations displayed on scan tool match identifications and locations recorded from special tool. If identifications and locations do not match, perform TPMS "Relearn Procedures."
3. Enable TPMS "learn mode." Use TPMS special tool in simulate mode to learn four simulated sensor transmissions into remote control door lock receiver. Verify all four sensor locations, identifications and tire pressures displayed on special tool match what scan tool displays. If scan tool does not match, replace remote control door lock receiver.
4. Drive vehicle at a speed above 25 mph for more than two minutes. Using scan tool, observe suspect "Pressure Sensor Mode" data parameter. Verify sensor mode changes from "Wake" to "Drive." If "Pressure Sensor Mode" does not change, replace suspected tire pressure sensor.
5. If no faults are found, proceed as follows:
  a. Aftermarket wheel valve stem holes may be located further from wheel rim than OEM wheels. When using tool No. EL-46079/J-46079, or equivalent, to activate sensor, ensure that antenna of tool is no further than six inches from sensor.
  b. TPMS Learn Procedure may require to be repeated up to three times before determining a sensor is faulty.
  c. Sometimes sensors locations may change due to tire rotations where TPMS Learn Procedure was not performed.
  d. Sometimes sensor transmissions will not be received due to vehicle level radio frequency interference.
  e. A sensor low battery condition will set a sensor DTC but will not illuminate low tire pressure indicator or display a message on DIC. Sensor battery condition can be verified in scan tool RCDLR data list. If a sensor low battery condition is indicated, sensor will require replacement.

DTC C0775 Low Tire Pressure System Sensors Not Learned

If the tire pressure sensor relearn procedure has not been performed, the TPMS indicator on the instrument cluster will flash for one minute and then remain On after the ignition switch has been placed in the ON position and the TPMS warning lamp bulb inspection has been completed. The DIC, if equipped, will also display a "service tire monitor" type message. Under these circumstances, DTC C0775 will be set and the relearn procedure will require to be performed for the system to function properly.
A current DTC will clear when the Relearn Procedure has been performed and one ignition ON cycle has occurred. A newly replaced RCDLR will set the DTC on its initial ignition ON cycle. The Relearn Procedure must be performed to clear the DTC.
If the DTC resets after performing the Relearn Procedure, replace the RCDLR.

Low Tire Pressure Indicator Fault

The RCDLR receives a RF transmission from each of the tire pressure sensors. Each of the sensors has a unique ID code which is transmitted as part of the RF message. These sensor IDs must be learned into the RCDLR memory. Once the four IDs have been learned into the RCDLR memory and vehicle speed is greater than 25 mph, the RCDLR will continuously compare the IDs received in the RF transmission to the IDs learned into memory to determine if all four sensors are present. If the RCDLR detects a low tire pressure condition or a fault in the system, it will send a message to the instrument panel cluster requesting the TPMS indicator to turn On and the appropriate data message to be displayed on the DIC.
Low tire pressure in one or more tires will be indicated by a continuously illuminated TPMS indicator after the bulb inspection has been completed. It is not required to perform the relearn procedure for a low tire condition.
When a TPMS DTC is set, the TPMS indicator icon will flash for one minute after the bulb inspection is completed and then will remain On. On models equipped with a DIC, a "service tire monitor" message will be displayed.
1. Inflate all tires to recommended pressure.
2. Drive vehicle at a speed over 25 mph for at least two minutes.
3. Ensure TPMS indicator is Off.
4. Connect GM tool No. EL-46079/J-46079, or equivalent, activate each tire pressure sensor and note each tire pressure reading.
5. Connect a known accurate tire pressure gauge, inspect air pressure of each tire.
6. Ensure tire pressure readings from GM tool EL-46079/J-46079, or equivalent, do not differ more that four psi from readings obtained with tire pressure gauge.
7. If readings differ more that four psi, replace indicated tire pressure sensor.
8. Connect a suitably programmed scan tool, enable TPMS "learn mode."
9. Connect GM tool No. EL-46079/J-46079, or equivalent, set in simulate mode to learn four simulated sensor transmissions into RCDLR. Note tire pressures indicated on scan tool display.
10. Ensure tire pressure readings from GM tool EL-46079/J-46079, or equivalent, do not differ more that four psi from readings on scan tool display.
11. If readings differ more that four psi, replace RCDLR.
12. Connect scan tool, perform instrument panel special functions lamp test. Command warning lamps On and Off. Ensure that TPMS warning indicator turns On and Off.
13. If TPMS warning indicator did not turn On and Off, replace instrument panel cluster.
14. Place ignition switch in ON position, then use scan tool to set up "Tire Type" and "Pressure Selection" in RCDLR module set up menu. Drive vehicle over 25 mph for at least two minutes.
15. Ensure TPMS warning indicator is Off.
16. If indicator is On, replace RCDLR.

Clearing Diagnostic Trouble Codes

Connect a suitably programmed scan tool to DLC (Data Link Connector), and follow manufacturers instructions.

Intermittent & Poor Connections

Intermittent Connections

Most intermittents are caused by faulty electrical connections or wiring. Inspect for the following:
1. Wiring broken inside insulation.
2. Poor connection between male and female terminal at connector.
3. Poor terminal to wire connection. Some conditions which fall under this are:
  a. Poor crimps.
  b. Poor solder joints.
  c. Crimping over wire insulation rather than wire.
  d. Corrosion in wire to terminal contact.
4. Wire insulation which is rubbed through. This causes an intermittent short as bare area touches other wiring or components.

Poor Connections

1. It is important to test terminal contact at component and any inline connectors before replacing suspect component.
2. Mating terminals must be inspected to ensure good terminal contact.
3. Poor connection between male and female terminal at a connector may be result of contamination or deformation.
4. Contamination may be caused by:
  a. Connector halves being improperly connected.
  b. Missing or damaged seal.
  c. Damaged connector.
  d. Exposing terminals to moisture and dirt.
5. Deformation is caused by:
  a. Probing connector terminal mating side without proper adapter.
  b. Improperly joining connector halves.
  c. Repeatedly separating and joining connector halves.
    Description
    The TPMS (Tire Pressure Monitor System) warns the driver when a significant loss or gain of tire pressure occurs in any of the four tires, and allows the driver to display the individua ...

    Relearn Procedures
    Keyless Entry Transmitter Or DIC Method 1. On models with standard ignition switch, place ignition switch in ON position. 2. On models w ...

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